This application is related to electrical switching apparatus and more particularly to sealed and insulated pressure actuated switching apparatus for use in swimming pools or the like to provide signals for race initiation and termination.
Electrical switching apparatus are employed in swimming races in order to start and/or stop the timing clock at the end of the race. These apparatus are generally pressure sensitive electrical switches which are secured to the side wall of the swimming pool. When pressure is applied to these switches by the swimmer, they will actuate providing an electrical current path to a clock or other timing device for controlling the clock and timing the race. These devices are more commonly known to swimming enthusiasts as swimming pool touch pads.
A touch pad presently being used consists of a pair of rectangular stainless steel screen-like elements separated by a very soft rubber sponge-like material, all encased in an insulated sheath with wires extending from the screen-like material. Pressure applied to one element through the insulated sheath will cause it to compress the sponge-like material until portions of that element extend through the openings in the sponge-like material and make positive contact at some point on the screen with the second screen-like element. In this touch pad, the sponge-like material deteriorates readily so that the touch pad is susceptible to a continuous shorting condition between the two screens after it has been used for an extended period of time. The density of the sponge-like material varies greatly as does its thickness so that prior to the degradation of this sponge-like material the difference in pressures necessary to force one element through the openings in the sponge-like material and against the other element causes different ones of this particular type of touch pad to have different sensitivities. Some are so insensitive that swimmers cannot put enough pressure on them in a normal manner to cause switching and conductivity and stop the timing clock. Also, the foam is in an air filled area that is always susceptible to leaks, resulting in shorting and contamination.
A second type of touch pad being used employs multiple aluminum plates pivotally secured by a pivot and hinges along the edge extending deepest into a swimming pool and slightly separated at the upper edge extending out of the pool. A microswitch is positioned adjacent the top edge and is actuated when pressure is applied to the outer plate by the swimmer causing it to pivot towards the inner plate and contact the microswitch. This apparatus is subject to deterioration due to corrosion of the pivot and hinges, and corrosion of the aluminum panels and microswitch. Again, as with the previously described touch pad, the most serious problem is insensitivity to pressure, resulting from the weight of the panels and the above noted corrosion inhibiting pivoting of the plates, so that a swimmer cannot actuate the touch pad; and relatively short useful life of the apparatus due to degradation. Due to the three dimensional nature of this construction, and the use of unprotected aluminum extruded sections, the swimmer runs a high risk of being cut or scraped during turns and finishes.
Neither style has the ability to be bent and still operate properly -- i.e., be sensitive on the top and on the front -- rather, with these alternate types, alternate means must be employed, such as ribbon switches, or more of the same construction in a parallel or perpendicular arrangement. These modifications increase the cost of the device.